Method of processing a tow of filamentary material



Nov. 7, 1961 BECKER ETAL 3,007,226

METHOD OF PROCESSING A TOW OF FILAMENTARY MATERIAL Original Filed Oct.6, 1959 -to a common assignee.

nited States Patent Original application Oct. 6, 1959, Ser. No. 844,741.

Divided and this application Nov. 28, 1960, Ser. No. 72,243

6 Claims. (Cl. 28-76) This invention relates broadly to the productionof a tow or strand of filamentary material, more particularly asynthetic filamentary material, and specifically a polyacrylonitrilefilamentary material, that is, one which is comprised of a polymer(fiber-forming polymer) of acrylonitrile. The invention is especiallyconcerned with certain new and useful improvements in a continuousmethod of producing a tow of a polyacrylonitrile filamentary material,advantageously one comprised of a polymer of acrylonitrile containing amajor proportion (preferably at least 75%) by weight of acrylonitrilecombined in the polymer molecule.

It was suggested prior to our invention that certain vegetable fibers(specifically cotton, hemp, jute, ramie and flax) and certainuncrosslinked thermoplastic synthetic fibers (specifically viscose andacetate rayons, nylon, fibers made from condensation products ofterephthalic acid and glycol, and fibers made from polyvinylidenechloride) be mechanically crimped while hot and then immediatelycrimp-set by cooling, while compacted under a substantially constantpressure, in a cooling zone of the same apparatus. Such a method andapparatus for practicing the same are described in, for example, RainardU.S. Patent No. 2,575,839.

A method of crimping and crimp-setting a tow of a polyacrylonitrilefilamentary material is disclosed and claimed in the copendingapplication of Mario Sonnino, Serial No. 545,043, filed November 4,1955, now Patent No. 2,960,752, dated November 22, 1960, and assigned Inthe specific crimp-setting technique therein described by way ofexample, the crimp is fixed by passing the tow of synthetic filamentarymaterial through a so-called J-box or other suitable receptaclecontaining cold water. The cold Water that is taken up by the tow(thereby forming a saturated tow) must subsequently be removed by asqueeze roll or other suitable device; and the removal of this entrainedwater may, under certain conditions, cause fiber entanglement andreduction of crimp amplitude. If no consideration be given to the tow asa final product, the squeeze roll or equivalent device may be by-passedand the crimp-set tow may be cut into staple While it containsapproximately 400% by weight of moisture. It is then necessary to formthe cut staple into a blanket which must be squeezed, separated orre-opened, and then conveyed to a staple dryer for drying the cutstaple.

Another method of crimp-setting a tow of polyacrylonitrile filamentarymaterial is described in Sellers U.S. Patent No. 2,874,446, datedFebruary 24, 1959. This method comprises continuously passing a tow ofsuch a material, and more particularly one comprised of a polymer ofacrylonitrile containing a major proportion by weight of acrylonitrilecombined in the polymer molecule, at a temperature of from about 150 F.to about 3,007,226 Patented Nov. 7, 1961 ice 200 F. directly from a towcrimper, wherein it has been hot-crimped mechanically, to a quenchingzone in which cooled gas (e.g., cooled air, nitrogen, flue gas, etc.) iscirculated. The tow-quenching apparatus or socalled tow quencher isseparate and distinct from the crimping apparatus, as a consequence ofwhich the hotcrimped tow is readily available for inspection prior tosetting of the crimp therein and the practical advantages of which willbe immediately apparent to those skilled in the art. The hot tow inrelaxed state is supported on a moving support, e.g., a continuouslymoving apron or screen formed of metal or other suitable material. Thissupport is preferably porous, e.g., by being provided with orifices orslots, or by the use of wire screening, so as to facilitate the passageof the cooled gas through the thusly supported tow. The supported,relaxed tow is passed continuously through the quenching zone. Thetemperature of the quenching zone and the time the tow is presenttherein are correlated so that the tow is at a temperature below F., andpreferably not higher than about 100 F., when it leaves the said zone.

The present invention has as its primary object an improvement in thecrimp-setting methods described above. It makes it possible to improvethe permanence of crimp of a tow of filamentary material that must beheated in order to be crimped, and to do this without materiallyaffecting the operation of the tow crimper; that is, while preventingback pressure on the stufiing box of the tow crimper that wouldmaterially aifect the uniformity of its operation.

The novel features of the invention are set forth in the appendedclaims. The invention itself, however, will be understood most readilyfrom the following detailed description when considered in connectionwith the accompanying drawing, which is illustrative of the invention,and in which:

FIG. 1 is a perspective view of the tow-quenching apparatus embodied inthe present invention; and

FIG. 2 is a side elevation and somewhat schematic view showing thetow-quenching apparatus (i.e., tow quencher) of the invention in itsrelationship to a tow crimper of the stufiing-box type and to apparatusused in a next step of the operation, specifically a J-box.

Referring to the drawing, a crimped tow 10 is led directly from a towcrimper 12, wherein it has been hotcrimped mechanically, to the towquencher 14 illustrated in more detail in FIG. 1. The tow is hot when itleaves the tow crimper, e.g., at a temperature of from about F. to about200 F. and, more particularly, about F. to about F. The hot, crimped towwhich is quenched in accordance with the present invention can be anytow of filamentary material which is hotcrimped mechanically, includingtows of natural and synthetic filamentary materials, numerous examplesof which were given in the second paragraph of this specification. Thus,the tow of filamentary material can be a tow of a polyacrylonitrilefilamentary material, e.g., one comprised of a polymer of acrylonitrilecontaining a major pro portion (advantageously at least 75%) by weightof acrylonitrile combined in the polymer molecule. Crimped tows of apolyacrylonitrile filamentary material containing 50%, or less than 50%(e.g., as little as 35 or 40%), by weight of acrylonitrile combined inthe polymer molecule, also can be processed in accordance with thepresent invention in order to set the crimp.

The continuously moving tow passes over the shelf 16 to the feed-in end18 of the primary slide 20. The hot tow, as it leaves the tow crimper,is generally wet with water and may contain, for example, from about 50%to about 150% by weight of water, based on the weight of the bone-drytow.

The primary slide 20 is open at its feed-in end, and is comprised ofbottom wall 22 (FIG. 1) and side walls 24 and 26 (FIG. 1). The primaryslide is provided with a slight dip as indicated; that is, it has aconcave bottom wall. This dip in the primary slide aids in keeping theslide wetted. The wetted primary slide facilitates preservation of theprimary and secondary crimp without exerting excessive back pressure onthe stufiing box of the crimper.

The hot, continuously moving tow 10' after it leaves the tow crimper 12is quenched with a cooling liquid 28, e.g., an aqueous cooling liquid ata temperature of from about 50 F. to about 100 F., and advantageouslysuch an aqueous cooling liquid which contains an antistatic agent.Cooling liquids at a temperature lower or higher than those justmentioned by way of example may be used as desired or as conditions mayrequire. However, the cooling liquid, as will be obvious to thoseskilled in the art, in all cases should be at a temperature materiallybelow, e.g., at least about 30-40 F. below, the temperature of thecrimped tow leaving the exit end of the tow crimper. The cooling liquidis applied by any suitable means, for instance through the nozzle orspray 30 located at the exit end of the conduit 32 which is fed with thecooling liquid from a supply source (not shown).

The cooling liquid is advantageously applied to the continuously movingtow at a point after it leaves the exit end of the tow crimper 12 and ator just before it passes onto the primary slide 20. Application of thecooling liquid to the continuously moving tow at a later stage of theprocess, e.g., while it is on the primary slide 20, is not precludedand, with certain hot-crimping techniques and certain types offilamentary materials, even may be desirable.

Any suitable antistatic agent may be a component of the liquid coolingmedium. Examples of antistatic agents which may be used are theguanylurea and guanidine salts of monoaliphatic hydrocarbon esters ofsulfuric acid, more particularly such salts wherein the aliphatichydrocarbon grouping contains from 12 to 18 carbon atoms, inclusive,e.g., guanylurea octadecyl hydrogen sulfate, guanidine octadecylhydrogen sulfate, guanidine oleyl hydrogen sulfate, etc. Still otherexamples of antistatic agents which may be used areB-alkoxypropionitriles, e.g., octadecoxypropionitrile; reaction productsof ethylene oxide and a long-chain alkyl guanamine, e.g., octadecylguanamine; and reaction products of ethylene oxide and a long-chainalkyl guanidine, e.g., octadecyl guanidine.

The antistatic agent may be the sole effect agent that is present, alongwith the liquid (e.g., aqueous) compo nent, in the quenching liquor; andsuch an agent may be one which is inherently capable of functioning bothas a lubricating agent and as an antistatic agent. In other cases it maybe desirable to use the antistatic agent in conjunction with otherconditioning or effect agents which are commonly employed in treatingsynthetic fibers, more particularly fibers produced from acrylonitrilepolymerization products. Such auxiliary conditioning agents includemineral, vegetable and animal oils, among which latter may be mentionedblown and unblown neats-foot oil, sperm oil, olive oil, teaseed oil,peanut oil, soya bean oil and cottonseed oil, as well as the varioussulfonated oils, e.g., sulfonated olive oil. Examples of otherconditioning agents that may be employed in conjunction with theaforementioned guanylurea salt or guanidine salt or other antistaticagent are wetting and dispersing agents and textile lubricants ofvarious kinds, for instance N- octadecyl disodium sulfosuccinamate,dioctyl sodium sulfosuccinate, lecithin, esters of long-chain fattyacids, e.g., alkyl stearates, palmitates and oleates, more particularlythe ethyl, propyl, butyl and amyl stearates, palmitates and oleates.

The shelf 16 is held in place by any suitable means, for instance bybeing supported on a suitable support (not shown), and is positionedslightly above and even with (i.e., in approximately the same verticalplane), or slightly forward of, the rod 34 upon which are mounted,preferably detachably mounted, the primary slide 20 at its feed-in endand the discharge slide or guide 36. The shelf 16 is preferably curvedat its forward edge and is positioned sufficiently close to the bottomwall 22 of the feed-in end of the primary slide as to permit thecontinuous movement of the tow of filamentary material from the exit endof the tow crimper to the primary slide of the tow quencher. Since theforward edge of the shelf 16 is slightly above the rod 34, and henceabove the edge of the bottom wall of the feed-in end of the primaryslide, there is a slight gap or opening therebetween.

By constructing and positioning both the shelf 16 and the primary slide20 as described above, the possibility of back flow of quenching liquor(cooling liquid) into the stuffing box of the tow crimper is obivated,as a consequence of which uniformity of temperature control in thecrimping operation is made possible. In other words, the open, sloped,primary slide 20, when positioned as described above with reference tothe exit end of the tow crimper and especially the shelf 16, preventsthe flow of quench liquor into the crimping zone and thereby providesobvious advantages that will be readily appreciated by those skilled inthe art.

The primary slide 20 is provided with arms 54 and 56 which are pivotallymounted as shown, that is, to the side walls of the primary slide, nearthe take-off end thereof, through the pivots 58 and 60, respectively;and are pivotally mounted at the other end on the supports 62 and 64.The pivot mounting on the support 62 is shown at 66. The arms 54 and 56permit the lowering or raising of the primary slide 20 and thus make itpossible to control the amount of liquid in the dip of the primaryslide.

From the primary slide 20 the tow 10 passes continuously to anadjustable secondary slide 38 having a bottom wall 40 and side walls,one of which is shown at 42. The secondary slide is pivotally mounted atthe takeoff end of the primary slide 20, and is adjustably attached atthe side walls thereof by means of the slotted arms 44 and 46 andcorresponding set screws (one of which is shown at 48) to the side walls24 and 26 of the primary slide.

The adjustable secondary slide 38 permits adjustment of the frictionaldrag on the continuously moving tow 10 which, in turn, controls thepoint, shown at 50, at which the tow changes from a folded form(so-called block form) to its normal or flat tow form.

From the foregoing it will be seen that the wetted, open, primary slideholds the tow in its crimped form while being quenched without exertingmaterial (i.e., objectionable) back pressure on the stutfing box of thecrimper. Additional or excessive back pressure is undesirable since itcan lead to too high a crimp and/or require an excessive force to feedthe tow into the crimper.) In addition, the sloping, wetted slides, moreparticularly the dip in the bottom wall of the primary slide, allows theattainment of an appreciable residence time with advantages that will bereadily appreciated by those skilled in the art. Furthermore, theconstruction and arrangement of the primary and secondary slides withrespect to each other provides a residence time that can be easilyadjusted as desired or as conditions may require.

The cap 52, mounted as shown at the end of the primary slide and overthe receiving end of the secondary slide, is advantageously employed toprevent the overflow of tow at the end of the primary slide.

The tow leaving the exit end of the adjustable secondary slide 38 islimited in its forward, and guided in its downward, motion by the lowerportion of the discharge slide or guide 36. From the secondary slide 38and/or the discharge slide or guide 36 the tow passes to the nextoperating step of the process, e.g., through the J-box 68 wherein it maybe suitably treated toimprove its useful properties, e.g., with water ata temperature of 98 C. to 999 C.

Although not limited thereto, our invention is particularly applicableto the processing of a mechanically hotcrimped tow of filamentarymaterial comprised of a polymer of acrylonitrile. The filamentarymaterial may be formed of a homopolymer or of a copolymer ofacrylonitrile. We may use, for example, a tow of filamentary materialcomprised of, for instance, a copolymer of about 95% by weight ofacrylonitrile and about 5% by weight of methyl acrylate; or a ternarypolymer of, by weight, about 88% acrylonitrile, about 6% of vinylacetate and about 6% of a vinylpyridine, e.g., 2-methyl-5-vinylpyridine.Other acrylonitrile copolymers (thermoplastic acrylonitrile copolymers)of which the tow may be composed or comprised, and after beinghot-crimped mechanically then used in practicing the present invention,are acrylonitrile oopolymers containing in the polymer molecules anaverage of, for example, at least about 35%, preferably at least about75 by weight of combined acrylonitrile. Taking as an example theexpression an acrylonitrile polymer containing in the polymer moleculesan average of at least about 35% by weight of combined acrylonitrile,this means herein a polymerization product (homopolymer, copolymer, orgraft polymer or mixtures thereof) containing in the molecules thereofan average of at least about 35% by weight of the acrylonitrile unit,which is considered to be present in the individual polymer molecule asthe group (iHa-O'H-CN or, otherwise stated, at least about 35% by weightof the reactant substance converted into and forming the polymerizationproduct is acrylonitrile. The expression an acrylonitrile polymercontaining in the polymer molecules an average of at least about 75% byweight of combined acrylonitrile has a similar meaning herein.

Illustrative examples of monomers which may be copolymerized withacrylonit-rile to yield a polymerization product containing in thepolymer molecules an average of at least about 35%, preferably at leastabout 75%, by weight of combined acrylonitrile are compounds containinga single CH =C grouping, for instance, the vinyl esters and especiallythe vinyl esters of saturated aliphatic monocarboxylic acids, e.g.,vinyl acetate, vinyl propionate, vinyl 'butyrate, etc.; vinyl halides,e.g., the vinyl chlorides, bromides and fluorides; allyl-type alcohols,e.g., allyl alcohols, methallyl alcohol, ethallyl alcohol, etc.; allyl,methallyl and other unsaturated monohydric alcohol esters of monobasicacids, e.g., allyl and methallyl acetates, laurates, cyanides, etc.;acrylic and alkacrylic acids (e.g., methacrylic, ethacrylic, etc.) andesters and amides of such acids (e. g., methyl, ethyl, propyl, butyl,etc., ,acrylates and methacrylates, acrylamide, methacrylamide,N-methyl, -ethyl, -propyl, -butyl, etc., acrylamides andmethacrylamides, etc.); methacrylonitrile, ethacrylonitrile and otherhydrocarbon-substituted acrylonitriles; unsaturated aliphatichydrocarbons containing a single CH =C grouping, e.g., isobutylene,etc.; and numerous other vinyl, acrylic and other compounds containing asingle CH =C grouping which are copolymerizable with acrylonitrile toyield thermoplastic copolymers. Alkyl esters of alpha, beta-unsaturatedpolycarboxylic acids also may be copolymerized with acrylonitrile toform using the Staudinger equation (reference: U.S. Patent The tow ofpolyacrylonitrile filamentary material may be produced from anacrylonitrile polymerization product by any suitable method and usingany suitable apparatus, but advantageously is produced as is describedin, for example, Sonnino Patent No. 2,849,751, dated September 2, 1958.

From the foregoing it will be seen that the present invention involvescertain new and useful method features constituting improvements in acontinuous method of producing a tow of filamentary material wherein thesaid tow has been hot-crimped mechanically. The method features comprisecausing the crimped tow, after it leaves the exit end of the towcrimper, to move continuously over a wetted surface; maintaining saidsurface in a wetted condition while the aforesaid tow is continuouslypassing over it, and controlling the frictional drag on the continuouslymoving tow thereby to control the point at which the said tOW changesfrom a folded or so -called block form to its normal tow form. In thepreferred embodiment the hot, continuously moving tow is quenched with acooling liquid, e.g., an aqueous cooling liquid such as one thatcontains an antistatic agent, shortly after it leaves the exit end ofthe tow crimper.

Specifically, the invention provides a method wherein the tow offilamentary material is maintained, while being quenched, in the form offolds of crimped tow without exerting material back pressure on thestuffing box of the tow crimper. In other words, the invention makes itpossible to prevent back pressure, while the tow is being quenched, onthe stufiing box of the tow crimper that would materially afiect theuniformity of operation of the tow crimper.

Another advantage of the invention is the fact that its use obviates orminimizes filament entanglement, knotting, etc., that occur or tend tooccur if a continuously moving, ho -crimped tow or strand, while stillhot, is exposed to blasts of cold air or other gas sufficient to coolthe tow quickly and to set the crimp.

This application is a division of our copending application Serial No.844,741, filed October 6, 1959.

We claim:

1. In a continuous method of producing a tow of filamentary materialwherein the said tow has been hotcrimped mechanically by a tow crimper,the improvement which comprises causing the crimped tow, after it leavesthe exit end of the tow crimper, to move continuously over a wettedsurface; maintaining said surface in a wetted condition while the saidtow is continuously moving over it; and controlling the frictional dragon the continuously moving tow thereby to control the point on saidwetted surface at which the said tow changes from a folded form to itsnormal tow form.

2. The improvement as in claim 1 wherein the tow which is processed is atow of filamentary material comprised of a polymer of acrylonitrile.

3. The improvement as in claim 1 wherein the tow of filamentary materialcomprised of a polymer of acrylonitrile is one wherein the acrylonitrilepolymer contains a major proportion by weight of acrylonitrile combinedin the polymer molecule.

4. The improvement as in claim 3 wherein the .acrylonitrile polymercontains at least 75% by weight of acrylonitrile combined in the polymermolecule.

'5. In a continuous method of producing a tow of polyacrylonitrilefilamentary material wherein the said tow has been hot-crimpedmechanically by a tow crimper, the improvement which comprises quenchingthe hot, continuously moving tow with a cooling liquid shortly after itleaves the exit end of the tow crimper; causing the crimped tow to movecontinuously over a wetted surface; maintaining said surface in a wettedcondition while said tow is continuously moving over it; and controllingthe frictional drag on the continuously moving tow thereby to controlthe point on said wetted 8 surface at which the said tow changes from afolded form to its normal tow form.

6. A method as in claim 5 wherein the cooling liquid with which thecontinuously moving tow is quenched is an aqueous cooling liquidcontaining an antistatic agent.

References Cited in the file of this patent UNITED STATES PATENTS2,669,001 Keen Feb. 16, 1954 2,712,977 Keggin July 12, 1955 2,734,229Shattuck Feb. 14, 1956

5. IN A CONTINUOUS METHOD OF PRODUCING A TOW OF POLYACRYLONITRILEFILAMENTARY MATERIAL WHEREIN THE SAID TOW HAS BEEN HOT-CRIMPEDMECHANICALLY BY A TOW CRIMPER, THE IMPROVEMENT WHICH COMPRISES QUENCINGTHE HOT, CONTINUOUSLY MOVING TOW WITH A COOLING LIQUID SHORTLY AFTER ITLEAVES THE EXIT END OF THE ROW CRIMPER; CAUSING THE CRIMPLED TOW TO MOVECONTINOUSLY OVER A